The present invention relates to a silicon oxide film evaluation method and apparatus for evaluating silicon oxide films formed on silicon substrates, and a semiconductor device fabrication method and apparatus using the evaluation method.
Silicon semiconductor devices, such as bipolar transistors, MOSFETs memory devices, etc., use as their insulating films silicon oxide films formed on silicon substrates by thermal oxidation. Among the silicon oxide films formed by thermal oxidation, field insulating films for device isolation are thick, but silicon oxide films used as gate insulating films and dielectric films of trench capacitors are very thin. But these thin films are required to be thinner as the semiconductor devices are more dense.
A film thickness of a thin oxide film of below about 10 nm formed by thermal oxidation corresponds to tens of atomic layers in terms of atomic layer. Accordingly it is preferred that film quality evaluation of the silicon oxide film is conducted by physico-chemical structural analyses, which are conducted on the atomic and molecular levels.
But the conventional evaluation method cannot evaluate silicon oxide films non-destructively and has to evaluate them based on electric characteristics of the semiconductor device. Electric characteristics of a semiconductor device is much influenced not only by thermal oxidation, but also by fabrication processing, such as electrodes formation, heat treatments, etc., which follows the thermal oxidation. For this reason it is impossible to correctly determine thermal oxidation conditions based on electric characteristics of a semiconductor device, and to determine proper thermal oxidation conditions, inefficiently trials and errors have to be repeated. This is a problem of inefficiency.
As methods for directly observing surface and interface states of semiconductor devices, atomic absorption spectrometry, Auger electron spectroscopies, infrared spectroscopic analysis, transmission electron microscopes, scanning tunneling electron microscopes, scanning atomic force microscopes, etc. are known.
In observations by atomic absorption spectrometry, Auger electron spectroscopies, infrared spectroscopic analysis, transmission electron microscopes, scanning tunneling electron microscopes, scanning atomic force microscopes, etc., samples have to be placed in a vacuum, and are broken. Accordingly semiconductor substrates under fabrication cannot be directly observed. It is necessary to put aside semiconductor substrates under fabrication for samples for the observation.
But actually surface states of the samples do not agree with those of the semiconductor substrates under fabrication for semiconductor circuits to be formed on. As a result, observation errors occur. It is necessary to secure a space for the samples in a semiconductor fabrication apparatus. As a result fabrication efficiency is lowered, and time and labor are needed. This is also a problem.
But infrared absorption analysis is a non-contact, non-destructive observation method and can be conducted in the normal atmospheric pressure. Because of these characteristics, infrared absorption analysis enables the semiconductor substrates of semiconductor devices under fabrication to be directly observed.
An object of the present invention is to provide a silicon oxide film evaluation method and apparatus which enable silicon oxide films formed on silicon substrates to be non-destructively observed in non-contact for evaluation.
Another object of the represent invention is to provide a semiconductor device fabrication method and apparatus which enables silicon oxide films formed on silicon substrates to be observed in line.